Field of Invention
The invention relates to a system and to a method for producing a rotor-blade spar cap with pultruded rods made of a fiber-reinforced material.
Brief Description of Related Art
Rotor-blade spar caps generally comprise thick strands of parallel fibers, usually glass fibers or carbon fibers, which are embedded in a resin matrix. The rotor-blade spar caps pass through the rotor blades usually over a large part of the rotor-blade length from the rotor-blade tip to the rotor-blade root and serve to transmit to the rotor-blade root the forces which act on the rotor blade.
Rotor-blade spar caps are produced usually in a layered construction in which either dry fiber fabrics are laid one upon the other with parallel orientation and are then made into the rotor-blade spar cap by resin infusion; or prefabricated layers of fiber materials already embedded in resin, so-called prepregs, are laid one upon the other and are then connected to one another. Since rotor-blade spar caps are of a similar length to modern rotor blades, that is to say possibly over 40 m or 50 m in length, the fiber materials used are correspondingly long and large in volume.
The operation of curing the resin is an exothermic process; heat is therefore produced. The heat distributed over large volumes may result in the formation of waves in the fiber material, and therefore the latter no longer has ideal parallel orientation over the entire spar-cap length. This then impairs the tensile strength and therefore the structural compactness and the functional capability of the rotor-blade spar cap produced in this way.
US 2011/0243750 A1 discloses the use of pultruded rods made of fiber-reinforced material instead of dry glass-fiber fabrics or prepregs. Such pultruded rods consist of a fiber-reinforced material which is produced by pultrusion and in which the glass fibers or carbon fibers have parallel orientation and are already embedded in a resin matrix. The pultrusion also provides the fibers with ideal parallel orientation. The pultruded rods are laid tight against one another to give the construction of the rotor-blade spar cap. Subsequent joining of the rods to one another no longer results in the formation of waves. The disclosure of US 2011/0243750 A1 is hereby incorporated by reference in its entirety as if fully presented in this application.
US 2012/0027609 A1 also discloses a method for producing rotor-blade spar caps from pultruded rods, wherein a quasi-endless pultruded rod is rolled up on a roll and unrolled. In this method, each layer is built up from rods which are unrolled one after the other from the roll, and cut off from the quasi-endless rod, before the next layer is built up, in turn, in the same way. Following completion, the contour of the respective end of each layer is finished off.
Proceeding from this prior art, it is an object of the present invention to specify a system and a method which are intended for producing a rotor-blade spar cap with pultruded rods made of a fiber-reinforced material and which make it possible to construct a rotor-blade spar cap with pultruded rods quickly, reliably and flexibly.